Transmembrane signaling plays a central role in all of biology, allowing cells to sense and respond to their environment. In humans, integral membrane receptors mediate the effects of hormones, neurotransmitters, cytokines, and a multitude of other signaling molecules. The PAQR receptors are a poorly characterized family of transmembrane receptors, found in organisms ranging from bacteria to humans. Recently, two PAQR receptors have attracted particular attention because they mediate the effects of a protein hormone called adiponectin. Adiponectin has been shown to induce profound insulin-sensitizing and cardioprotective effects in mouse models of diabetes and cardiovascular disease, but little is known regarding the molecular mechanisms of adiponectin signaling. To unravel the molecular details of adiponectin receptor signaling, we will pursue a combination of structural and biochemical studies of adiponectin and its receptors, with the long term goal of developing a detailed molecular understanding of signaling through the adiponectin receptors and broader PAQR family.